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What Happens to a head in a Machine Shop


Galant VR-4 org Post #: 1139646 posted 09/09/13 09:51 AM     Remind Me!  Send Private Message   Edit Post      
What Happens to a head in a machine shop

First Not all shops have the same equipment and the procedures from one shop to the next can and will differ.
Some shops cater to domestics and others imports or even diesels.
Some shops will view everything as a “stock” rebuilds.
The most important thing to know is the shop you use and the equipment they will use.

The subject head is a Mitsubishi 4G63 7 Bolt

The first thing that should happen is the machinist looks at the head. Checking for the obvious damage, broken bolts, stripped bolt holes, bent valves, ect.

At this point it is up to you as the customer, inform the shop what you want done, such as…
1) Pressure test for cracks
2) Valve job
3) Surface
4) Guide work
5) Any performance work wanted
Also now is the time to speak about who will provide what parts, valves, seals, guides, springs, ect.

Now the shop should be able to give you, the customer, an approximate estimate of what the parts and labor will cost.

You as the customer have the choice to agree, or go somewhere else.
Now that your head is at the machine shop, and you have agreed to have the work done.

The first thing to happen is the head will be disassembled.

The tools needed are

Wire basket for small parts springs, valves, ect
Small container for valve locks
Valve lock release tool (socket method)
10mm socket
12mm socket
12mm socket
5.5mm allen bit socket or wrench
Pocket magnet
Long reach needle nose pliers w/45* bend
Impact gun (not pictured)

Cam gears come off first, use impact with the 17mm socket

Next remove the cam tower caps, use impact or ratchet w/12mm socket.
Start at the ends working towards the center

Once the cam caps are removed, lift the cams out.

Next lift the roller followers out

Now you can remove the HLA’s

Now remove the oil spliter

Now remove any other small bolts

This is a “heat tab” Most machine shops use them.
The center will slide down at 240-250* and totally dissolve at 260*

Next is to remove the valve train.
Yes the same method that a lot of DIY people use are used in a machine shop.
Use a basket and a paint cap, have a pocket magnet handy too.

Have your “tool” and hammer ready to go
Place the tool on the spring retainer and give it a firm whack.
The locks will stay in the tool and release the retainer and spring.
Place the retainers and spring in the basket

Fish the valve locks out of the head casting with the pocket magnet.

Place the valve locks in the paint can cap.

Now remove the spring seats with the pocket magnet and place in the spring basket to be cleaned.

Next roll the head over and remove the valves and place in the basket.

This head was rebuilt once before, it must have had bent valves.So I will change the valve guides.
Now roll the head back over and remove the valve stem seals, throw these in the trash.

Next grab the 5mm allen bit and remove all the oil galley plugs. Keep these to be installed later, place in the paint cap with the valve locks.

The last thing done is to remove the cracked valve guides.

Now that the head is fully stripped, it can be tech’ed
First thing is to do a quick clean on the head gasket surface.

Next is to measure head thickness.

Now to check to see how bad the head is warped.

Notes are taken to reference back too.

If it all checks out, it goes to cleaning.
It gets thermal cleaning, then glass beaded.

Next oil port mod #1 is done

Next all the oil galleys get gun brushed

Now the entire head will be blown off with compressed air, including every bolt hole to make sure there is no glass bead media is left in or on the casting.

next is a coat of spray paint to seal the casting.

Now new guides can be installed.

They are set to height.

Now the valve seats can be cut.
Fist is to set the head in the machine and secure it properly.

The proper sized pilot is selected.

The head is now leveled in the machine.

Now to set up the seat cutter.
First is to find where the seat is to make contact on the valve.

Now the cutter bit can be set.

The seats are cut.

Now the valves are lapped.

The small parts of he head have been cleaned, retainers, springs ect.

Valve springs are tested.

Most valve springs have been found weak, so New BC1100 springs will be installed
(stock spring on left, BC spring on right)

A broken exhaust stud was found and removed.

The valves are ground.

Ground and ready to be installed.

Now the head can be surfaced.
The head is set up and secured to the milling machine.

The proper surface finish is milled for the head gasket to be used.
(a composite for this one) You can see that this head was belt surfaced before.

The head is now blown out to remove metal flake from milling and seat cutting.

Now that the machining is done, it is time to assemble the head.

Valve tip height is checked to make sure it is in spec.

The valves are removed, lubed up and slid back into the same hole they came from.

A package of valve seals found in a head gasket set.

Now the seals are pushed on by hand

Now seals can be installed, this is my “hi-Tech” seal installer.

Now the seals are tapped into place securely.

Now spring shims are installed if needed.

The spring shim goes on before the spring seat.

Now the cleaned spring seats are installed.

On top of the spring shims.

The new valve springs, BC1100

Now the new BC1100 springs are placed in the head, on the spring seat.

I will set the head back in the TnS 2000 Seat and guide machine, Using this adapter I will compress the valve springs.

Now before I compress the spring, I will take the valve spring retainer.

Install the valve locks,

Then place it on top of the spring.

Now with the spring and retainer compressed,

I can push the valve locks into place.

Repeat the process till all the springs and locks are seated properly.

Now this customer is going to install new 3g HLA’s. So no need for me to install the last of the valve train.
I check the valve to seat seal one last time.

I did install the cam tower caps on their proper side and position.
Each cam tower bolt received a quick dip in oil, since all the bolt threads are dry.

Now the oil galley plugs received a dab of sealant.

Then started by hand to prevent cross threading.

Then tighten to seal.

I measure the head for thickness and make a not of how much was removed.

The final step is to CC the combustion chamber so proper compression ratio can be calculated.

This head is now done, and ready for the customer to pick up and install.

Edited by BogusSVO (09/18/13 04:58 AM)

Posts: 232 | From: Pensacola, Florida | Member Since: 08/29/13 | IP: ( | Report this post to a Moderator

G Galant Moderator
JDM Unit

Galant VR-4 org Post #: 1139672 posted 09/09/13 12:15 PM     Remind Me!  Send Private Message   Edit Post      
Looks good, but we need to get you a camera with an easy to use focus.

Posts: 8896 | From: zompton | Member Since: 02/24/04 | IP: ( | Report this post to a Moderator


Galant VR-4 org Post #: 1139673 posted 09/09/13 12:19 PM     Remind Me!  Send Private Message   Edit Post      
That camera died about a year ago.

I have another one I use now, and learned what the macro mode is!

Posts: 232 | From: Pensacola, Florida | Member Since: 08/29/13 | IP: ( | Report this post to a Moderator

Victory Runner

Galant VR-4 org Post #: 1139773 posted 09/10/13 08:01 AM     Remind Me!  Send Private Message   Edit Post      

I have to ask a couple of other questions. Basically because I'm that kind of a person and the environment I work in and the way I work we have to build out risk.

Also because I take pride in the work I do wrenching on the projects I do. Not hating just trying to help out.

A shop and the way it is kept tells more about the method of work than any other story. I will always assemble my own stuff from any shop work here's why:

1) Your strip bench is filthy. Although you are cleaning later I don't see any effort to keep debris out of the vitals. Once oilways are plugged (and there's a few on a head) you can have blind boreways it's impossible to clean. Any shite will come out later in oil flow and destroy any oil film or get into what you don't want to.
2) Media blasting: again it's sacreligeous that there is no attempt made to control the media. That shit will bunch and get everywhere. I use it for external/simple cleanable parts only Where there are no ground working or porous surfaces. I don't see any effort to clean using any wet media/solvent's. My favorites are carb and brake cleaner. If I'm working on stuff I'll generally pick up a case or two and get things straight and clean before proceeding any further.
3) Using an air wrench to remove the Cam gears. Have you ever sheared a Cam knock pin? I'm sure there will be some that are stepped because of this. On a 4G63 Use a spanner and soft block to lock the cam. then I use in addition a motorcycle clutch boss locking tool to steady the gear and a good size wrench to 'feel' the nut loose.
4) The oil you are using to lube up on reassembly. Could you have found a more contaminated container to dispense from? Surely you want the oil going in clean and fresh and with no particulate to score or wear anything.
5) ALWAYS hand lap the valves in.. just to conform the evenness of the valve seats.
6) Rusty spring retainers. Now you could use a bung to guard the collet surface and blast them.

As I said I do all my assembly myself. I have trusted people who I will work with and no offense there are shops like you who I will on occasion take stuff to also.

But that said the If the head in the pics was mine I'd want it torn down again to lap the valves Clean ALL residue off and out of the oilways and I'd start assembly again.

We are a technical community. We do a lot of work ourselves and we all take pride in the board. Your how to's are informative I'm sure if you read up on me I'm sure you'll find holes to pick, but here in this technical section but please take a bit of pride in the way you do your work.

Another word of advice from working in high volume precision manufacturing. If you have good quality tools they will only be good quality tools as long as you look after them. The beds, and slides will wear fast if you don't keep the shit out of them and all pictures above look like a small amount of housekeeping will go along way.

I hope you take this as positive advice, because I want to show others what we should expect and watch for.

In our hobby it is possible that all our good effort could be rendered scrap by a stray swarf or contaminant or simply not cleaning oil galleries correctly or a cylinder bore properly after honing.

Hope this helps,


92 UK 1800 GALANT DD
88 JDM E39A GALANT VR-4, running. But only just.
93 CB4A --- rewound
91 PDM GTI Resurection project. Aborted
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Posts: 1558 | From: Midlands, UK | Member Since: 08/04/04 | IP: ( | Report this post to a Moderator

It's no Mirage, man

Galant VR-4 org Post #: 1139787 posted 09/10/13 09:35 AM     Remind Me!  Send Private Message   Edit Post      
Great job man! Quick question though. I know if you even mention a blast cabinet around some people with a valve cover or something you will hear that it's impossible to get every last bit out after it's blasted. What is different with a cylinder head? I would think down in the hidden passages where old oil was would attract the glass bead. Is there a thorough way to get this out?

Edit: Seems Rich beat me to it.

Edited by 89Mirageman (09/10/13 09:40 AM)

Posts: 2502 | From: Stantonsburg, NC | Member Since: 07/05/06 | IP: ( | Report this post to a Moderator


Galant VR-4 org Post #: 1139790 posted 09/10/13 09:52 AM     Remind Me!  Send Private Message   Edit Post      
Yes the tear down area is a horrid area to even attempt to keep clean. By the time to you tear down two to 10 heads, loose oil and grime gets every where I will agree.

There is a step missing between tear down and glass beading, that is the thermal cleaning of the head, When a part is thermal cleaned, it is cooked so all liquid is burnt dry and turns to a powder.

On some heads there will be blind oil galleys, but a .22/.25 cal copper gun brush works best to insure the galleys are clean. If there is a hole I feel that may have an issue I do flush with brake clean. Now I will agree if a head is washed in a vat or spray cabinet that it should never be inside a glass beader.

In 20 years of burning heads and glass beading them, I have not had a head come back or get cussed out over leaving grit in any oil passage and locking up a cam or causing a cam journal issue. So I am comfortable with the cleaning procedures I have in place.

As far as shearing a dowel pin on a cam, I can not recall a single one ever shearing off. Not just on the 4g engine, but even on the divit style cam gears such as the dodge 4.7 SOHC.

Yes that paint cap was nasty, they normally get pitched every 2 or 3 days, the cap is only used to lube cam tower bolts, not cams, cam journals, or buckets. I have a pistol grip oiler I use for that.

Hand lapping is not needed with decent equipment, Now back in the day when stone seat grinders were the norm, and left burrs on the seat I will agree the seats need lapped. But with the modern dead pilot systems, and 3 angle carbide cutters seat run out can be held to less than .001 on a 2 inch valve. If there is a valve seal issue it will show up in the vac test. I look for a min of 27 inches of vac with out the springs installed.

The reason for the flash rust was I had a sales rep come in and demo'ed a new cleaner for my spray cabinet, come to find out it did not have the rust inhibitors in it, so I went back to my old product, so that is not a issues except on 2 or 3 heads, and the rust wiped off with a basic red shop towel.

I may not work in a high volume shop like you do, I am a 1 man shop with a part time guy in teardown. But we do take one day a week to clean the machines and the ways. I have found over the years that Turtle wax car wax is the best, unlike oil, grease that will hold grit, that the car wax will let it "float" so it cam be blown off.

Posts: 232 | From: Pensacola, Florida | Member Since: 08/29/13 | IP: ( | Report this post to a Moderator

Victory Runner

Galant VR-4 org Post #: 1139921 posted 09/11/13 09:33 AM     Remind Me!  Send Private Message   Edit Post   
As I said posts like these show more about you than you can know.

1) Maybe you missed the step of cleaning but it's pretty fundamental. And as you posted it's no one else who missed it.
2) I don't care how much you justify it the bench with all the swarf and shit and the box of new valve springs on in undeniable, as is the mess on the strip bench. not to mention inexcusable.
3) Maybe you wax the slides but the rust on the wheel shafts on the seat cutter and the threaded stops etc says there isn't alot of maintenance there.
4) Maybe you don't lap the seats, but you cannot use the same cutter to do the seats and the valves together, and the wheel you do the valves with is only as good as the dressing it's recieved and the prep you do. Therefore they cannot be spot on. Again I have issue with the evidence I see. I sir would be lapping for surity.
5) I mentioned the cam pins as I've acutially had them shear on me,
6) Even if it is oil on the cam cap bolts, there is no excuse for the shit state of the cap and oil, period. At 10-11Nm you have a good percentage down to thread friction. Oil with lumps of shit in it is not a slippy as clean oil. Thats why we use clean oil.
7) Even if it was a lapse in the hot tank, you are still installing rusty parts in the photos you chose to post.

Maybe you've been doing this 20 years, but when did you decide to stop improving? Should always be looking for a better way. No?

In 1997 I finally laid my hands on a YZ490, I picked it up from a little backwoods race engine shop out in the sticks near where I grew up in Essex. They prepped mostly Rootes and early Ford and Lotus stuff and there shop was a pleasure to be in. clean and intimate.

A little about me:
Yes I work in volume manufacturing now, but I flunked college because I was making lots of mistakes and learning lots of stuff working in my local two man motorbike shop. The kind that is small but has a very wide coverage. Ferdy (the lead partner) was so well respected through his work and through his connections you would not believe the cool stuff we had come through the shop and the experiences. I learned so much it's impossible to write. I've spent my university years building and selling mountain bikes and motorcycles and working in motocross shop in Leicester building engines because the shop owner didn't want to. Hell I didn't even buy a car till 1999.

I've since worked as a development engineer at Cummins making and developing 3000+ bhp mine truck engines and Rolls royce designing test equipment on a drawing board for jet engines. Since uni I've worked in the aerospace industry straight through. As a development engineer qualifying parts to fly, as a desiner designing whole flight controls and systems, As a researcher... hell I even have my name on a patent.

I'm now working heavily involved in the manufacturing side of the business and all the way through everywhere one thing is constant.

Learn and Improve.

Yes people may not return stuff, but I know the things I pointed out in what you chose to post. hence I raised them.. I probably wouldn't I'd probably just go someplace else.

I am, we all are here to help each other out. And adjust each others course when we see it on the wrong heading.

Hope you understand,


92 UK 1800 GALANT DD
88 JDM E39A GALANT VR-4, running. But only just.
93 CB4A --- rewound
91 PDM GTI Resurection project. Aborted
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Posts: 1558 | From: Midlands, UK | Member Since: 08/04/04 | IP: ( | Report this post to a Moderator

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